1. Field of the Invention
The invention is related to apparatus, compositions and methods for separating the phases of aqueous suspensions by centrifugal force and more particularly is related to the centrifugal separation of serum or plasma from whole blood.
2. Brief Description of the Prior Art
Prior hereto, blood separator devices have been known which employ non-Newtonian fluids as the separator barrier component; see for example U.S. Pat. Nos. 3,780,935 and 3,852,194 which employ barrier materials described as "gel-like" or "thixotropic".
In general, the blood separator devices of the prior art type employing a fluid separator component have not been entirely satisfactory in all respects. This is particularly true of pre-assembled units wherein the fluid barrier is initially disposed in the blood collection container component. Such pre-assembled units are subjected to handling, transportation and storage under a wide variety of environmental conditions prior to their use. Under handling, the fluid barrier component of some such assemblies may flow, coating the interior of the collection container, prior to operation of the device. This is undesirable because contact with the collection container (usually glass) facilitates the desired clotting of collected blood.
In the ideal blood separator of the type employing a non-Newtonian fluid as the phase separation barrier component, the fluid may be characterized as (1) compositionally stable, (2) physically stable in the absence of a substantial centrifugal force, (3) forming a strong, cohesive barrier, (4) chemically inert and (5) having a density intermediate between that of the separate blood phases. By compositionally stable, it is meant that the components or ingredients of the barrier material will not separate under normal storage and/or use. For example if the fluid separator is basically an oil or an oil-like composition compounded with an inert filler, the separator composition should be stable in that the oil or oil-like material should not bleed or separate from the inert filler dispersed therein. By physically stable, it is meant that the barrier material should not move or change shape except when subjected to a substantial centrifugal force. The barrier material, except when subjected to a substantial centrifugal force, should form a strong, cohesive body. By chemically inert, it is meant that the barrier material should not be chemically reactive with blood, its constituents or reagents commonly employed in carrying out diagnostic testing of blood serum.
My invention constitutes an improvement over the prior art in that I have provided a blood separator and blood separating compositions having the desired features of an ideal blood separator. The method of my invention provides a more reliable operative procedure. In addition and unexpectedly the compositions and assemblies of my invention are advantageously sterilized by exposure to ionizing radiation without significant degradation of composition or assembly.